[machinist_1]

I think runing your lathe in reverse wil break the tip of your tool.

Just a thought.

[kawazuki]

I think runing your lathe in reverse wil break the tip of your tool.

Just a thought.

Only maybe unless you back it out on the cross slide? Even if you don't the negative rake below the cutting point won't touch the work and it certainly won't cut anything

[machinist_1]

You are right about that, (backing off with the cross slide). But, even with a neg. rake there is still a small amount of tool deflection when you make a cut. So runing in reverse will cause the tool to drag along the part.

[fourxblz]

That works fine if you can guarantee you have absolutely zero backlash between spindle and leadscrew!

I think leaving the half nuts engaged will negate any worries with backlash, therefore the cutting tip should run in the exact same place. I only say this because I got much better and more consistent results.
I'm not saying to not back out the cross slide. It's one of those things where I tried it and didn't have any ill effects from doing so. Note that I've only done that while taking light cuts while doing fine threads.

[kawazuki]

I think leaving the half nuts engaged will negate any worries with backlash, therefore the cutting tip should run in the exact same place. I only say this because I got much better and more consistent results.

Its not leadscrew backlash you need to worry about - its all those gears between the leadscrew and the spindle - it could be significant which would put the new cut thread out of 'step' with the cutter? But at the end of the day - whatever works for you, do it!